ECG interpretation

Question 1

What can ECG show us?

Answer 1

Electrical activity recorded ONLY the pump may have stopped working and electricity is still going!

Assessment of rate and rhythm

May provide evidence of chamber enlargement/hypertrophy

May suggest altered myocardial metabolism

Question 2

What is the rate of this ECG?

Answer 2

Question 3

What is the rate of this ECG?

Answer 3

Question 4

Rhythm interpretation things to think of?

Answer 4

What is the rate?

Is it regular or irregular?

If irregular- is it irregularly irregular or regularly irregular?

Is there a P wave for every QRS complex?

Is there a QRS for every P?

Are the Ps and the QRS5 consistently and similarly related?

Are all the Ps alike?

Are all the QRSs alike?

Are the QRSs narrow and upright in leads 2/3/AVF .

Are the QRS5 wide and bizarre?

Question 5

What is a normal sinus rhythm?

Answer 5

NORMAL SINUS RHYTHM (N.S.R.)

• Normal impulse originates in the S.A.N.
• The S.A.N. has an inherent pacemaker rate of:
  
  • 70-160 b.p.m in the dog
  • 160-240 b.p.m in the cat
• P waves are usually positive in lead II.
• The PR interval is usually consistent from beat to beat . The QRS complex is usually “normal”
• The rhythm may be regular or irregular

Question 6

Discuss sinus arrhythmia?

Answer 6

SINUS ARRHYTHMIA.

• As N.S.R. except greater variation in P-P interval.
• The rhythm is irregular- regularly so
• If related to the respiratory cycle
  
  • RESPIRATORY SINUS ARRHYTHMIA
  • normal rhythm in the dog, abnormal in the cat mediated by fluctuations in vagal tone and no innervation of the sympathetic system.
    
    • Abolished by atropine accentuated by vagal manouveres.

Question 7

How does a bundle branch block occur?

Answer 7

Question 8

What is sinus arrest?

Answer 8

Sinus arrest

• The failure of pacemaker to discharge
• Pause with no P-QRS-T complex
• Heart does not stop!
• Next fastest pacemaker takes over
• AV node then ventricular cells
• Cardiac cells and automaticity

Question 9

What has occured here in this sinus arrest?

Answer 9

Question 10

What is persistant atrial standstill?

Answer 10

Persistent atrial standstill

• There is a complete absence of P waves
• Next fastest pacemaker takes over
• The heart rate is usually slow but regular
• QRST - normal - junctional escape rhythm

Question 11

Look at this persistant atrial standstill?

Answer 11

Question 12

What is a 1st degree AV block?

Answer 12

First degree AV block

• P wave and QRS complex are normal
• The P-R interval is prolonged

Question 13

What is a second degree AV block?

Answer 13

Second degree AV block

• P wave not conducted through the AV node
• P without QRS

Question 14

What is a complete (third) degree AV block?

Answer 14

Complete (third degree) AV block

• Persistent failure of conduction through AV node
• Ventricles usually paced from ventricular focus
• Wide, bizarre escape complexes at approx 30-40/mm (dog)

Wide bizarre complexes QRS odd shape. Bizarre as myocytes are contracting in ventricles and causing electrical depolarisation. Affecting shape of QRS complex. It is not the AV node causing the ventricles to contract but the intrinsic rhythmicity of ventricle pacemakers themselves.

As nothing from SAN and AVN are coming down the ventricles (which are pacemakers themselves) get time to cause their own contraction.

It’s a problem with the AV node. But the SA node is working as we have a P wave.

SA and AV nodes are the Ferrari and usually trigger the ventricle depolarisation and are quick but if they don’t trigger the ventricles you have to wait for the bus to turn (ventricle pacemakers) up which is slower but still causes the contraction and takes a less direct route than the Ferrari.

Question 15

What is an ectopic rhythm?

Answer 15

An ectopic rhythm is an irregular heart rhythm due to a premature heartbeat. Ectopic rhythm is also known as premature atrial contraction, premature ventricular contraction, and extra systole.

Question 16

Discuss tachydysrhythmias?

Answer 16

• Heart rate higher than “normal”
• Ectopic activity
• Origin of abnormal activity
  
  • Supraventricular
    
    • Atria
    • AV Junction
  • Ventricular

Question 17

What are supraventricular premature complexes?

Answer 17

SUPRAVENTRICULAR PREMATURE COMPLEXES

• A premature P wave (P’ wave) interrupts normal P wave rhythm
• P’ wave is early (compared with the normal P-P interval)
• P’ wave configuration differs from the normal P waves
• QRST usually normal

Question 18

What is supraventricular tachycardia?

Answer 18

SUPRAVENTRICULARTACHYCARDIA is when:

• Runs of more than three consecutive supra ventricular Premature Complexes
• Heart rate during tachycardia is greater than upper normal limit
• Rhythm during tachycardia is usually regular though but slower because site of origin is still SAN
• Site of origin is within the atria/junction, outside the SAN.
• P’ waves differ from the “normal” sinus P wave (if available) because the P
• Maybe sustained (>30s) or non-sustained (paroxysmal, <30s)
• P’-P’ interval is normally regular.
• P’-R interval is normally constant IF every P’ wave is conducted
• QRS is usually “normal” — narrow and upright in Lead 2

Question 19

What is atrial fibrillation?

Answer 19

ATRIAL FIBRILLATION (AF)

• Heart rate may or may not be within normal limits
• Rhythm is irregularly irregular
• No isoelectric baseline
• No P waves
• Irregular, variable amplitude F waves may be evident . QRS complex is usually “normal” - narrow, upright in Lead 2
• Usually sustained, maybe non-sustained (last for less than 30 secs) (paroxysmal)

No isoelectric baseline it I constantly being electrically stimulated by myocytes in atria not all these signals are conducted by AV but some random firings are causing wibbles.

Question 20

What are ventricular premature complexes?

Answer 20

• A.k.a. ventricular ectopics
• Site of origin is within the ventricles
• Rhythm is irregular
• Wide & bizarre QRST complex interrupts rhythm
• Spread through myocardium, NOT conducting tissue
• Usually the underlying Normal Sinus Rhythm is undisturbed
• VPC QRST unrelated to P waves
• VPC QRST complex voltage is usually large

Question 21

Look at these ventricular premature complexes?

Answer 21

Gap between each contraction suddenly gets shorter with wide bizarre complexes.

Interruptions by early ventricular contractions.

Go from normal, cut short with odd complex to cut short.

Question 22

Look at these ventricular ectopic complexes?

Answer 22

Triplet pattern of abnormalities interrupting NSR.

When it is wide and looks weird that will be something caused by the ventricles.

Question 23

Look at this ventricular tachycardia?

Answer 23

No P wave

Question 24

What is ventricular fibrillation?

Answer 24

VENTRICULAR FIBRILLATION

• Usually terminal
• Rhythm associated with cardiopulmonary arrest
• Heart rate rapid and irregular
• No isoelectric baseline
• ECG is irregular and chaotic
• No recognisable PQRST complexes
• Course or fine depending on the degree of baseline oscillation

Question 25

What is mean electric axis?

Answer 25

* MEA (mean electrical axis) is used to measure chamber enlargement and asses for bundle branch blocks. * You need to choose your isoelectric lead, which is the lead which basically has the straightest line with the least deviation in height (lead whose positive and negative areas cancel out) * Go to your funny circular diagram thing, and then choose the line which is perpendicular (crosses it 90 degrees) to your isoelectric lead. * Looking at the graph which corresponds to your perpendicular line on the ECG, is it predominantly positive or negative? If it is positive, choose the positive value from your perpendicular line, this is your answer.

Question 26

Look at this?

Answer 26

Question 27

Look at this chart?

Answer 27